Jupiter's mass is 317.8 times Earth, equatorial radius is 11.209 times Earth, that gives gravity = 2.528 times Earth so 54 kg x 2.538 = 137 kg. If your teacher is a stickler for accuracy, kilograms are a measure of mass, and Newtons are a measure of weight. So 54 kg weigh 54 x 9.81 = 530 Newtons ...